Explosive shell and method of making the same



A. LEFERE EXPLOSIVE SHELL AND METHOD OF MAKING THE SAME Filed June 6, 1938 g ly?! .ALJDUF' LEFEFPE INVENTOR A TTZZRNE V6 Patented Dec. 12, 1939 EXPLOSIVE SHELL AND METHOD OF MAKING THE SAME Alidor Lefere, Jackson, Mich., assignor to Lefere Forge & Machine Company, Jackson, Mich., a corporation of Michigan Application June 6, 1938, Serial No. 212,162

5 Claims.

The present invention relates to the production of relatively heavy tubular articles having a closed end and more particularly to high explosive shells.

5 Heretofore high explosive shells. have been produced commercially by forcing a mandrel through a steel billet to provide a tubular blank having a closed end. This method has not been satisfactory for the reason that not only is a poor 10 grain structure developed by the drawing action,

but also-because it has been impossible to force a mandrel in a straight path through the billet.

The result of the eccentric hollow interior of the blank caused by the failure of the mandrel to 15 keep a straight path, and of the provision of suflicient metal in advance of the mandrel to prevent the same from forcing its way through the end of the blank, has been that the rough blank was often fully twice the weight of the fin- 20 ished shell after machining. In fact, it not infrequently happened that hydraulically pressed blanks had to be scrapped entirely due to the extreme eccentricity of the interior opening. High explosive shells: to be most efiective should 25 break into a large number of relatively small particles; 'The reason is that not only is a better coverage obtained, but also smaller particles are more likely to wound than kill, and 1mm a military point of view the seriously wounding of one 30 person is "ust as effective against the enemy as the killing outright of several persons. The grain structure resulting from pressing a high explosive shell, is such that the shell upon explosion breaks into a relatively small number of pieces 35 of a character that are more likely to kill than to wound. A forged high explosive shell has a very fine grain which breaks upon explosion into a great many small pieces and therefore is of a greater military value than a pressed high explosive shell. However, heretofore it has been impossible to forge high explosive shlls because of problems arising in their manufacture which have been impossible to solve. The present invention contemplates the manufacture of high 45 explosive shells by the forging from a billet or slug of a hollow blank, conical in form, then swinging the sides of the blank-inwardly until they are substantially cylindrical, and finally drawing the swung in blank to slightly lengthen 5 the same to provide the shell ready for machin- According to the present invention, only a slight amount of machining is required to produce the finished shell.

'55 Another feature of the invention contemplates the provision of cleavage lines within the high explosive shell to insure substantially uniform breaking upon the explosion of the shell.

An object of the invention is to manufacture high explosive shells or the like by forging. 5 Another object of the invention is to provide a new method of forging tubular articles, which comprises forging a conical blank and swinging in'the sides of the blank.

A still further object of the invention isto provide a method of internally grooving tubular bodies, which comprises swaging a tubular body over a ridged mandrel.

These and other objects will be apparent from the following specification when taken with the accompanying drawing, in which Fig. 1 illustrates a billet from which the firstblank is forged,

"Fig. 2 is a vertical section of the first forged blank associated with tools for swinging in the sides,

Fig. 3 is a vertical section of the blank of Fig.

-2 after the sides have been swung in, associated with tools for drawing the same,

Fig. 4 is a vertical section of the blank of Fig. 3 after it has been drawn,

Fig. 5 is a vertical section of the blank of Fig.

4 after it has been trimmed and is ready for final machining,

Fig. 6 is 'a vertical section illustrating an embodiment of the invention, wherein a specific mandrel is employed for the purpose of forming in the interior of the shell a series of axially extending grooves,

Fig. '7 is a vertical section of the blank of Fig. 6 having circumferentially extending grooves machined therein,

Fig. 8 is an elevation of the mandrel employed in the formation of the shell disclosed in Fig. 7, and 40 Fig. 9 is a section on the line IX-IX of Fig. 8.

Referring particularly to the drawing, the reference character I represents a cylindrical billet or slug which may be cut from cylindrical rolled bar stock, but preferably is formed by cutting off a section from. a square rerolled billet and then reducing it to cylindrical shape by forging. A cast slug would not be particularly satisfactory because of the large grain structure. The slug I is heated to a suitable degree and then forged. 5 between suitable dies to provide a hollow conical blank 2 as disclosed particularly in Fig. 2. The conical blank 2 is closed at its smaller end and has a flash 3 comprising the excess metal forced out between the forging dies. The side walls of the conical blank 2 are inclined at a sufficient angle to its vertical axis to require a male forging die of sufficient dimension to withstand the heat to which it is subjected as the result of being surrounded by the hot metal during the forging of the blank 2. One of the reasons why it has heretofore not been possible to forge an explosive shell has been that it has been impossible to produce a long narrow male die which would stand up under the heat to which it is subjected, during the forging while it is surrounded by hot metal. According to the present invention, a relatively long and narrow male die for forging is not required. It has been found that if the angle between the inside wall of the conical blank 2 and the vertical axis thereof is of the order of eight and one-half degrees that satisfactory results can be produced. The blank 2 as disclosed in Fig. 2 is drawn approximately to scale and illustrates dimensions that have been found satisfactory for the so-called three inch explosive shell. The full size overall length of the blank 2 disclosed in Fig.

2 is seven and one-sixteenth inches.

After the blank 2 has been forged, it is placed on a mandrel 4 provided with a shoulder 5. The length of the mandrel 4 is such that when the end thereof abuts against the inner end of the blank 2, the open end of the blank 2 rests against the shoulder 5. The mandrel l and the shoulder 5, carrying the blank 2, are then moved through a sizing ring 6 to swing in the sides of the blank 2. At the same time, a trimming ring 6 is moved ahead of the sizing ring 6 to shear off the flash 3. These operations produce the blank 7 shown in Fig. 3. It will be observed that the shoulder 5 just fits through the sizing ring 6. It will be understood that at the start of the swinging in of the sides of the blank 2 by the sizing ring 6, that the open end of the blank 2 will 'just seat on the outer edge of the shoulder 5, and that as the sides are swung in, the open end of the blank 2 will slide inwardly of the shoulder 5. While in the drawing there is illustrated only one sizing ring 6, it is contemplated that, if desired two or more sizing rings 6, operative in succession, may be used.

As shown in Fig. 3, the blank 'I is placed on a mandrel 8. It is then forced through a drawing ring 9 to elongate the blank I and to reduce it to true cylindrical outline, providing the blank I0. It will be understood that in place of a single drawing ring 9 several successively operating rings may be employed in the usual manner, if desired.

The mandrels 4 and 8 are extremely rigid and serve to act with the rings 6 and 9 respectively to true the work should at any stage of the operation the blanks have deviated from their true .f or! n. The mandrels 4 and 8 should have a diametr such, that there is about one thirty-second of an inch clearance between them and the blanks after their respective operations have been com pleted. This clearance will prevent any binding of the mandrels but at the same time the mandrels are effective to prevent the possible formation of an internal protuberance.

While the sides of the blank are being swung in to form the blank 1 disclosed in Fig. 3, the shoulder 5 prevents any drawing or elongating of the blank 2. Accordingly, there is some upsetting of the wall sections. The walls of the blank 1 are therefore thicker than the walls of the blank 2, and due to the working, have a finer grain structure. The blank I is about nine inches long for the :ize of shell illustrated and therefore is slightly under two inches longer than the original blank 2. This small amount of drawing does not destroy the fine grain structure obtained by forging. The blank I0 is disclosed in Fig. having the rough open end trimmed off and ready for final machining. The blank i0 is almost of the exact overall dimensions required and is not only in the neighborhood of fifty per cent lighter than the hydraulically pressed blank heretofore known, but also since only a small fraction of the machining formerly required is necessary, a large saving in labor is effected and a product having a fine grain has been provided. It is preferred that each of theoperations be carried out during a single heat. However, reheating of the blanks may be resorted to if required.

Figs. 6, 7, 8 and 9 relate to an embodiment of the invention. Broadly, this embodiment contemplates the providing of an explosive shell as above described with the addition of internal grooves or cleavage lines to define lines of fracture when the shell explodes, thereby insuring a minimum number of fragments. According to the present embodiment of the invention, the blank '7, formed as above described, is placed on a mandrel l5 provided with a series of axially extending uniformly spaced ridges I6. The blank I is then forced through the drawing ring 9 or its equivalent, swaging the blank I about the ridges 16 providing a blank I! having therein a series of axially extending grooves I8. The blank l'l after it has been removed from the mandrel l5 is machined to provide a series of circumferentially extending grooves l9, shown in Fig. 7, of substantially the same depth as the grooves l8. While the ridges [6 have been disclosed as of V-shaped cross-section, it is contemplated that theymay have any cross-section which is desired.

It is to be understood that the dimensions given hereinabove are by way of example only and are not to be considered as limiting the invention in any manner. The forged explosive shell, according to this invention, has a uniform, fine grain structure, the result of which is that when the shell is exploded it breaks into a relatively large number of substantially uniform sized pieces. The invention while particularly adaptable to explosive shells may be used in the production of other tubular articles, for instance, wheel hubs. In the case of wheel hubs the drawing step can be dispensed with.

Having thus described my invention, what I desire to secure by Letters Patent and claim is:

1. Inthe manufacture of heavy tubular members such as shells and the like, forging a hollow blank having a conical form, the smaller end thereof being closed and the other end being open, radially swinging in the sides of said blank while supporting the same at the inside of the closed end and at the open end, and drawing the swung in blank to elongate the same.

2. In the manufacture of heavy tubular members such as shells and the like, forging a hollow blank having a conical form, the smaller end thereof being closed and the other end being open, radially swinging in the sides of said blank while supporting the same at the inside of the closed end and at the open end, and drawing the swung in blank over a mandrel to elongate the same.

3. In the manufacture of heavy tubular members such as shells and the like, forging a hollow blank having a conical form, the smaller end thereof being closed and the other end being open, said blank having a flash, radially swinging in the sides of said blank while supporting the same at the inside of the closed end with a mandrel and at the open end, and at the same time shearing oil? said flash, and drawing the swung blank over a mandrel to elongate the same.

4. In the manufacture of heavy tubular mem bers such as shells and the like, forging a hollow blank having a conical form, the smaller end the closed end and at the open end.

for providing a shell structure having the ability 5 to break into a plurality of relatively small pieces free from assistance of lines of weakness resulting from fabrication,

ALDDORLEFERE 1o 

